Letter (Astounding, October 1939): The Movement May Be Merely a Short-Time Variation, Though; Ice Ages Mean Thousand-Year Periods.
| First published | October 1939 |
|---|---|
| Type | Essay |
| Date | Publication | Publisher | Type | Page | |
|---|---|---|---|---|---|
| October 1939 |
|
Astounding Science-Fiction, October 1939 | Street & Smith Publications, Inc. | MAGAZINE | 160|160.3 |